This invention relates to filtering systems for filtering or straining fluids and in particular to a filter system having changeable filter elements with filter media for any degree of filtering and providing for uniform distributed flow through all parts of the filter element.
Fluid filtering systems with changeable filter elements for different degrees of filtering are known in the art. Filtering systems are known which include a generally tubular filter basket having a body comprising the desired filtering medium, a closed bottom and an open top. The basket is mounted in a filter housing in the fluid stream such that flow is through the sides of the basket to the outlet. The prior art basket includes a flange at the top of the basket. The basket is secured to a flange ring fixed in the housing by bolts through the basket flange threadably engaging with the housing ring flange. Several problems are apparent in the prior art. Filter elements of the elongate basket type are inconvenient and difficult to remove from the filter housing. The means for retaining such baskets in the filter housing restricts the size of the filter basket. The range of filter element materials and filtering actions is limited to coarser less fragile filtering media. And, plugging of the filter element or basket causes the concentration of flow through the basket at a certain area.
Removal of the filter basket is difficult as a number of bolts must be removed and replaced to change it. Corrosion of the bolts or housing flange threads make removal of the bolts even more difficult.
Bolting the basket to a flange also restricts the size of the basket useable in the housing. The housing flange must necessarily have sufficient width to be bored and threaded to accept the bolts, sufficient clearance must be allowed between the housing and the bolt heads to facilitate their removal, and the diameter of filter basket that will fit in the housing flange is limited by these conditions.
Limitations on the filtering media comprising the filter basket is another problem in the prior art. Vibrations caused by flow of fluid through the basket cause flutter and fatigue in the filter media, causing it to break or fail. The use of fine or fragile filtering media in filter baskets has therefore been limited. When the flow is pulsating or intermittent, stress on the filter basket is increased and the problem aggravated. Heretofore, use of fragile sintered metal filter media has been confined to relatively small filters.
Pegging of the filter element or basket is also a problem in the prior art filter system. Pegging occurs when the inlet flow is directed against a particular part of the basket and flow is not uniformly distributed about the basket. In such case, one part of the basket receives a greater part of the total flow through the basket than the other parts of the basket. As a result, that part of the basket becomes clogged or dirty before the other parts of the basket. Optimally, the pressure at and flow through each part of the filter medium of the basket should be uniform.